Method for forming a photovoltaic module

Abstract

According to the present invention, a method for forming a photovoltaic module is disclosed, the photovoltaic module comprising an intermediate film for a backsheet for photovoltaic modules comprising a substrate film, for example, a PET film, and a partially cross-linked layer of coating resin. The method includes providing a substrate film, depositing and spreading a layer of coating resin on the substrate film, and partially cross-linking the layer of coating resin. According to this method, the cross-linking of the resin is stopped before it is completed so that the intermediate film is obtained, and it is finished during the subsequent process of laminating the intermediate film to the encapsulant of a photovoltaic module.

1 . Method for forming a photovoltaic module including a backsheet and an encapsulant, said method including the following steps, performed in the order in which they are listed:
 a) providing a substrate film;   b) depositing a layer of coating resin on said substrate film; and   c) cross-linking said layer of coating resin, wherein said cross-linking is divided into the following two successive sub-steps:   c1) partially cross-linking said layer of coating resin, so as to obtain an intermediate film comprising said substrate film covered by a layer of partially cross-linked resin wherein said partial cross-linking is obtained by interrupting cross-linking after a predefined time interval less than the time for completing the cross-linking reaction; and   c2) laminating said intermediate film to said encapsulant;   wherein during said step c2) of lamination the completion of cross-linking of said partially cross-linked resin layer takes place so as to obtain a fully cross-linked resin layer,   wherein said fully cross-linked resin layer acts as an adhesive between said substrate film and said encapsulant.   
     
     
         2 . (canceled) 
     
     
         3 . The method according to  claim 1 , wherein said coating resin comprises a blocked cross-linking agent having an unblocking temperature and capable of inducing partial cross-linking of said layer of coating resin upon exposure to a temperature equal to or greater than said unblocking temperature. 
     
     
         4 . Method according to  claim 3 , wherein said unblocking temperature is comprised between 100° C. and 120° C. 
     
     
         5 . Method according to  claim 3 , wherein said blocked cross-linking agent includes the blocking agent di-ethyl-malonate (DEM). 
     
     
         6 . Method according to  claim 3 , wherein said blocked cross-linking agent is a blocked aliphatic isocyanate. 
     
     
         7 . Method according to  claim 1 , wherein said coating resin comprises a cross-linking agent and all of said cross-linking agent is blocked by means of a blocking agent. 
     
     
         8 . Method according to  claim 1 , wherein said partial cross-linking of said step c1) is interrupted after a time interval comprised between 10 seconds and 25 seconds. 
     
     
         9 . Method according to  claim 1 , wherein said partial cross-linking is carried out to obtain an intermediate film comprising a layer of partially cross-linked resin, in which the cross-linking percentage is between 20% and 80%, wherein said cross-linking percentage is measured by performing an isothermal Differential Scanning calorimetry (DSC) analysis. 
     
     
         10 . Method according to  claim 1 , wherein said step c1) of partial cross-linking occurs by exposure of said intermediate film to a temperature in the range of 100° C. to 150° C. 
     
     
         11 . Method according to  claim 1 , wherein said coating resin comprises an acrylic resin with acrylate functionality. 
     
     
         12 . The method according to  claim 1 , wherein said substrate film is activated by means of a surface treatment, e.g., a corona treatment, a plasma treatment, and/or a chemical etching treatment, prior to said step b), so as to facilitate adhesion of said coating resin layer to said substrate film. 
     
     
         13 . Method according to  claim 1 , wherein said coating resin layer comprises pigments capable of absorbing visible light and transparent to infrared (IR) rays. 
     
     
         14 . The method according to  claim 1 , wherein said layer of coating resin comprises a solvent to enable workability of the mixture of said coating resin, and said method further comprises the following step:
 d) evaporation of said solvent,   wherein said step c1) is carried out during said step d).   
     
     
         15 . Method according to  claim 1 , wherein said partial cross-linking occurs by means of UV activation. 
     
     
         16 . Method according to  claim 1 , wherein said method is carried out by means of a reel-to-reel process. 
     
     
         17 . The method according to  claim 10 , wherein said lamination step c2) occurs by exposure of said intermediate film to a temperature in the range between 140° C. and 170° C. 
     
     
         18 . Method according to  claim 1 , where said step b) occurs along a coating line and said step c1) of partial cross-linking occurs along said coating line. 
     
     
         19 . The method according to  claim 9 , wherein the cross-linking percentage is between 35% and 40%. 
     
     
         20 . The method according to  claim 17 , wherein said lamination step c2) occurs by exposure of said intermediate film to a temperature in the range between 140° C. and 160° C.